IEEE C802.16m-09/1888r1
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
Proposed Changes to Handover Procedure (15.2.5.10/15.2.7.2.9)
Date
Submitted
2009-08-28
Source(s)
Kelvin Chou, Yih-Shen Chen, I-Kang Fu and
Paul Cheng
Kelvin.Chou@mediatek.com
MediaTek Inc.
jscha@etri.re.kr
Jaesun Cha
ETRI
Re:
Letter Ballot #30 on the Draft Amendment (IEEE P802.16m/D1)
Abstract
This contribution proposes some clarification to the MCHO section
Purpose
Propose to be discussed and adopted by TGm for the 802.16m Amendment
Notice
Release
Patent
Policy
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represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for
discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material
contained herein.
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and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name
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<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and
<http://standards.ieee.org/guides/opman/sect6.html#6.3>.
Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and
<http://standards.ieee.org/board/pat>.
Proposed Changes to Handover Procedure (15.2.5.10/15.2.7.2.9)
Kelvin Chou, Yih-Shen Chen, I-Kang Fu and Paul Cheng
MediaTek Inc.
I. Introduction
P802.16m/D1 has defined so many HO features as follows:
-
Single-carrier HO (15.2.7);
-
EBB HO using HO Reentry Interleaving Interval (15.2.7);
-
EBB HO using multiple carriers (15.2.9.2.9);
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-
HO with secondary carrier pre-assignment (15.2.9.2.9).
Besides, several parameters regarding the above HO features have been defined in the MAC management
message section (15.2.6) and in the Multi-Carrier HO section (15.2.9.2.9.2.3) as follows:
-
HO_Reentry_Mode (15.2.6.9 AAI_HO-CMD)
-
HO Reentry Interleaving Interval (15.2.6.9 AAI_HO-CMD)
-
MCHO Indication (15.2.6.9 AAI_HO-CMD)
-
Multi-Carrier_Support (15.2.9.2.9.2.3.5 AAI_HO-REQ in multi-carrier section)
-
Carrier Preassignment Indication (15.2.9.2.9.2.3.5 AAI_HO-REQ in multi-carrier section)
-
Multi-Carrier Indication (15.2.9.2.9.2.3.6 AAI_HO-CMD in multi-carrier section)
However, current definitions for the above parameters are ambiguous, and how to trigger each HO features
through the above parameters is not clear. This contribution proposes a clarification and summary of the
relationships among these HO features and parameters, which is illustrated in the following table:
HO Reentry Mode
Carrier Preassignment
Indication
0
1
HORII* > 0
HORII* = 0
0 single-carrier HO (15.2.7)
single-carrier EBB HO within
HORIIs (15.2.7)
multi-carrer EBB HO (15.2.9)
single-carrier HO (15.2.7)
with
1
secondary carrier
preassignment (15.2.9)
single-carrier EBB HO within
HORIIs (15.2.7)
with
secondary carrier
preassignment (15.2.9)
multi-carrer EBB HO (15.2.9)
with
secondary carrier
preassignment (15.2.9)
*HORII: HO Reentry Interleaving Interval
Based on the above table, text modification regarding general HO procedures and MCHO procedures are
proposed in this contribution, while text modification regarding HO MAC messages is provided in C802.16m09/1886 or the latest revision thereof.
II. Proposed Text
{Apply the following text modification to P802.16m/D1, Section 15.2.5.10.3 at page 95, line 54 as follows:}
---------------------------------------------------------- Text Start --------------------------------------------------------------15.2.57.10.3 HO Preparation
During HO preparation phase, the serving ABS communicates with target ABS(s) selected for HO. The target
ABS may obtain AMS information from the serving ABS via backbone network for HO optimization.
During HO preparation phase, the target ABS may allocate a dedicated ranging code or opportunity to the AMS
via the serving ABS through the AAI_HO-CMD message. The target ABS shall select the dedicated ranging
code from the group of codes which are allocated for handover purpose. After the target ABS sends the selected
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dedicated ranging code/opportunity to the serving ABS over the backhaul, the serving ABS shall deliver the
dedicated ranging code/opportunity to the AMS in AAI_HO-CMD.
Information regarding AMS identity (e.g.STID) or security context (e.g., nonce), may be pre-updated during HO
preparation. Any mismatched system information between AMS and the target ABS, if detected, may be
provided to the AMS by the Serving ABS during HO preparation. If pre-allocated at target ABS, the serving
ABS shall include an STID to be used at target ABS in the AAI_HO-CMD message. The pre-allocated STID
shall be used in the target ABS by the AMS to communicate with the target ABS. The FIDs which are used to
distinguish different connections are not updated during the handover procedure. Rejection of each service flow
shall also be indicated in the AAI_HO-CMD message.
If HO_Reentry_Mode is set to 1, the serving ABS shall negotiate with the target ABS the HO_ReentryEBB HO
parameters. In the single carrier handover case, the EBB HO parameters include the
HO_Reentry_Interleaving_Interval and HO Reentry Iteration information used in serving ABS for the AMS to
communicate with the serving ABS during network re-entry. In the multi-carrier handover case, the EBB HO
parameters include the carrier information in the target ABS for the AMS performing network reentry while
continuing communication with the serving ABS concurrently.
When only one target ABS is included in the AAI_HO-CMD message, the HO preparation phase completes
when serving ABS informs the AMS of its handover decision via an AAI_HO-CMD message. When multiple
target ABSs are included in the AAI_HO-CMD message, the HO preparation phase completes when the AMS
informs the ABS of its target ABS selection via an AAI_HO-IND message with code 1. The AAI_HO-CMD
message shall include an Action Time of each target ABS for the AMS to start network re-entry at each target
ABS. The AAI_HO-CMD message shall also include a Disconnect Time Offset for AMS to calculate
disconnect time for each candidate target ABS. When HO_Reentry_Mode is set to 0, the Disconnect Time shall
be set to the Action Time in the AAI_HO-CMD message will be (Action time - Disconnect Time Offset); For
HO_Reentry_Mode = 1, Disconnect time will be (Action time + Disconnect Time Offset).
The AAI_HO-CMD message indicates if the static and/or dynamic context and its components of the AMS are
available at the target ABS.
15.2.57.10.4 HO Execution
HO execution starts with AAI_HO-CMD message and ends at AMS's beginning to perform network re-entry at
Action Time. If HO_Reentry_Mode is set to 0, The serving ABS stops sending DL data and providing UL
allocations to the AMS after expiration of the disconnect time derived from Action Time and Disconnect Time
Offset included in the AAI_HO-CMD message or upon receiving AAI_HO-IND with HO Event Code 0b10,
whichever occurs first. If HO_Reentry_Mode is set to 1, the serving ABS stops sending DL data and providing
UL allocations to the AMS upon expiration of the disconnect time or after receiving HO completion
confirmation from target ABS, whichever occurs first.
If HO_Reentry_Mode is set to 0, at the expiration of Disconnect Time, the serving ABS shall start the
Resource_Retain_Time from value Resource_Retain_Time provided by ABS in AAI_REG-RSP or AAI_HOCMD messages.
The default Resource_Retain_Time indicated in AAI_REG-RSP is used unless AAI_HO-CMD provides
Resource_Retain_Time. If AAI_HO-CMD includes Resource_Retain_Time, the value include in AAI_HOCMD shall be used instead of the value included in AAI_REG-RSP. The serving ABS shall retain the connections, MAC state machine, and untransmitted/unacknowledged data associated with the AMS for service
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continuation until the expiration of the Resource_Retain_Time.
If the AAI_HO-CMD message includes only one target ABS, the AMS shall execute the HO as directed by the
ABS, unless, during HO execution or network re-entry, the AMS finds that the target ABS is unreachable as
defined in the 'target ABS unreachable condition' in section 15.2.5.2. The serving ABS defines conditions based
on which the AMS decides if it is unable to maintain communication with the serving ABS. If the AMS decides,
based on these conditions, that it cannot maintain communication with the serving ABS until the expiration of
Disconnect Time, the AMS may send and AAI_HO-IND message with HO Event Code 0b10 to the serving
ABS. If the AAI_HO-CMD message includes more than one target ABSs, the AMS shall select one of these
targets and informs the S-ABS of its selection by sending an AAI_HO-IND message with HO Event Code 0b00
to the S-ABS before the expiration of Disconnect Time.
The serving ABS defines error conditions based on which the AMS decides when a target ABS among those
that are included in the AAI_HO-CMD message is unreachable. These error conditions are defined as triggers
with action code 0x54, as specified in section 15.2.57.2
If all the target ABSs that are included in the AAI_HO-CMD message are unreachable, and if the AMS has a
preferred target ABS not included in the AAI_HO-CMD message, the AMS informs the serving ABS of its
preferred target ABS by sending AAI_HO-IND message with code 2 before the expiration of Disconnect Time,
and the AMS performs network re-entry at the new target ABS as indicated in the AAI_HO-IND message. The
AMS shall also indicate the BSID of its old serving ABS and previous used STID to the new target ABS during
network entry at the new target ABS.
If the AAI_HO-CMD message includes no target ABS, or if all the target ABSs that are included in the
AAI_HO-CMD message are unreachable as defined above, the AMS shall inform the serving ABS of it's
preferred target ABS by sending the AAI_HO-IND message with HO Event Code 0b01 before expiration of
Disconnect Time. If a serving ABS receives the AAI_HO-IND message with HO Event Code 0b01, it shall
respond to the AMS by sending AAI_HO-CMD with a target ABS which may include the target ABS proposed
by the AMS in the AAI_HO-IND message. The AMS shall wait until receiving the AAI_HO-CMD message
before expiration of Disconnect Time unless the AMS cannot maintain communication with the serving ABS as
defined above. If the AAI_HO-CMD message includes no target ABS, the Disconnect Time defines the deadline
by which the AMS shall respond by sending AAI_HO-IND to the serving ABS.
An AMS may request bandwidth for the residual data in the buffer before the expiration of Action Time. The
serving ABS may send information about any unallocated requested bandwidth to the target ABS over the
backhaul so that the target ABS may allocate uplink resource immediately after receiving the dedicated ranging
code from the AMS or after Action Time if CDMA ranging is omitted.
--------------------------------------------------------- Text End --------------------------------------------------------------{Apply the following text modification to P802.16m/D1, Section 15.2.5.10.5.2 at page 99, line 15 as follows:}
------------------------------------------------------- Text Start ---------------------------------------------------------------15.2. 57.10.5.2 Network Re-entry Procedure
The network re-entry procedure with the target ABS may be optimized by target ABS possession of AMS
information obtained from serving ABS over the backbone network.
At the Action Time specified in the AAI_HO-CMD message, the AMS performs network re-entry at the target
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ABS.
If HO_Reentry_Mode is set to 1, the AMS performs network re-entry with the target ABS at action time while
continuously communicating with the serving ABS. However, the AMS stops communication with serving ABS
after network re-entry at target ABS is completed. In addition, AMS does not exchange data with target ABS
prior to completion of network re-entry. In the single carrier handover caseIf HO_Reentry_Interleaving Interval
> 0, the AMS communicates with the serving ABS during HO_Reenry Interleaving_Interval, and with the target
ABS using the remaining communication opportunity. In the multi-carrier handover caseIf
HO_Reentry_Interleaving Interval = 0, AMS performs Multi-carrier EBB HO re-entry procedure per
15.2.9.2.9.2.2.1network reentry while continuing communication with the serving ABS concurrently via
multiple radio carriers. Upon completion of network reentry, the target ABS informs the serving ABS to stop
allocating resources to the AMS and release AMS context.
The network re-entry procedure is depicted in Figure 406 (HO_Reentry_Mode = 0) and Figure XX3407
(HO_Reentry_Mode = 1) respectively. This procedure corresponds to the block arrow entitled "Network Reentry" in Figure 404 and is described in detail in the following.
AMS
T-ABS
AAI_MSHO-REQ
AAI_BSHO-CMD
AAI_HO-IND
(dedicated) CDMA ranging code
AAI_RNG-RSPACK
Unicast encrypted DL data and/or UL grant
Unicast encrypted UL data and/or BW request
Ranging initiation deadline
Action time
- STID preupdate
- Security context
preupdate
- Ranging code
assignment
S-ABS
AAI_RNG-REQ (CMAC)
Target ABS becomes
Serving ABS
AAI_RNG-RSP (CMAC)
Completion of
NW re-entry
Figure 406 Network re-entry procedure with HO_Reentry_Mode set to 0. Messages depicted with dotted lines
are transmitted only in certain HO scenarios. The dash-line (optional) AAI_RNG-RSPACK carries time
adjustment parameters, etc.
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AMS
- STID preupdate
- Security context
preupdate
- Ranging code
assignment
T-ABS
AAI_MSHO-REQ
Action time
AAI_BSHO-CMD
AAI_HO-IND
(dedicated) CDMA ranging code
AAI_RNG-RSPACK
Maintain data communication
with S-ABS during
NW re-entry
Ranging initiation deadline
Disconnect time
S-ABS
AAI_RNG-REQ (CMAC)
Target ABS
Becomes serving ABS
AAI_RNG-RSP (CMAC)
Completion of
NW re-entry
Figure 407 Network re-entry procedure with HO_Reentry_Mode set to 1. Messages depicted with dotted lines
are transmitted only in certain HO scenarios. The dash-line (optional) AAI_RNG- RSPACK carries time
adjustment parameters, etc.
--------------------------------------------------------- Text End ---------------------------------------------------------------
{Apply the following text modification to P802.16m/D1, Section 15.2.7.2.9.2 at page 125, line 42 as follows:}
------------------------------------------------------- Text Start ---------------------------------------------------------------15.2.79.2.9.2 Multi-carrier handover (MCHO) procedure
The multi-carrier handover (MCHO) is defined as the handover procedure which involves multiple radio
carriers, which includes multi-carrier EBB HO (15.2.9.2.9.2.2.1) and HO with secondary carrier pre-assignment
(15.2.9.2.9.2.2.2), as described in this section.
15.2.79.2.9.2.1 MCHO preparation
An AMS in multi-carrier operation follows the handover operations defined in 15.2.67.2. MAC management
messages in relation with handover preparation and initiation between the AMS and the serving ABS are
transmitted over the primary carrier of the AMS.
During HO preparation, the AMS may request or be requested by the serving ABS to perform MCHO procedure
through AAI_HO-REQ/AAI_HO-CMD messages. The serving ABS informs the AMS the carrier information
(e.g. target primary carrier index) of the target ABSs through AAI_HO-CMD message. The serving ABS may
communicate with the target ABS(s) to help the AMS obtain the assigned secondary carriers before handover
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execution. The serving ABS will forward the information received from AAI_MC-REQ message to the target
ABS for secondary carrier pre-assignment. The serving ABS will reply the secondary carrier pre-assignment
results to the AMS if Carrier_Preassignment_Indication is set to 1 in the AAI_HO_CMD message. AMS may
also include Carrier_Preassignment_Indication in AAI_HO-REQ message to request to perform multi-carrier
EBB HO with secondary carrier pre-assignment (Carrier_Preassignment_Indication=1) or without secondary
carrier pre-assignment (Carrier_Preassignment_Indication=0).
15.2.79.2.9.2.2 MCHO execution and network re-entry
15.2.9.2.9.2.2.1 Multi-carrier EBB HO re-entry procedure
The AMS with multi-carrier capability follows the network re-entry procedure per section 15.2.67.2.5. When
HO_Reentry_Mode is set to 1 and HO_Reentry_Interleaving_Interval is set to 0, the AMS performs network reentry to the target ABS on one carrier and maintains normal communication with the serving ABS on another
carrier not performing network re-entry procedure. The AMS may use the original primary carrier for network
re-entry to the target ABS, as illustrated in Figure 426. It may also use another carrier different from its original
primary carrier for network re-entry procedures, as illustrated in Figure 427. In both cases, if the Multicarrier_Mode and HO_Reentry_Mode in AAI_HO-CMD message is are set to 1, the AMS maintains normal
communication with the serving ABS on another carrier not performing network re-entry procedure. In this case,
Disconnect_time should be long enough that network reentry procedure to target ABS can be completed prior to
the expiration of Disconnect_time. In case of AAI_HO-CMD message with multiple target ABS and carriers,
the physical index of each candidate carrier provided by each target ABS should also be indicated in the
AAI_HO-CMD message The AMS may inform the serving ABS through AAI_HO-IND the carrier to be used
for network re-entry operations to avoid resource allocation by the serving ABS on that carrier.
{No change to Figure 416}
{No change to Figure 417}
From AMS point of view, if network entry is completed (see 15.2.67), the AMS shall stop communicating with
the serving ABS. Then, the AMS may send UL data or BW-REQ message to the target ABS.
15.2.9.2.9.2.2.2 HO with secondary carrier pre-assignment
The serving ABS may negotiate with the target ABS for secondary carrier pre-assignment. In this caseWhen
Carrier_Preassignment_Index is set to 1 in the AAI_HO-CMD message, the pre-assignment information is
forwarded to the AMS by the serving ABS through AAI_HO-CMD message, and part of the pre-assigned
secondary carriers (indicated by the Carrier Status Bitmap) may be activated if the AMS sends AAI_CM-IND
message to the target ABS right after network re-entry. Before secondary carrier pre-assignment, the serving
ABS shall forward the multi-carrier capability of the AMS to the target ABS via backbone.
{No change to Figure 418 }
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If secondary carrier pre-assignment is not allowed, then When Carrier_Preassignment_Index is set to 0 in the
AAI_HO-CMD message, the AMS follows the operation of secondary carrier assignment (see 15.2.9.2.3.2) and
carrier activation (see 15.2.9.2.11.1) after the AMS completes its network re-entry with the target ABS.
------------------------------------------------------------ Text End ---------------------------------------------------------------
8